throttle; no response sometimes

[grave77]

Finally we have an 8 board in bimmer :)

it just happened few days ago, I can't really ideantify what's going wrong, but I sometimes go over 200Km/h and I feel no more accelaration until I remove my foot off the accelarator then step again then it cont. to accelarate. any idea what's wrong? last week my car just gave an EML light and lost lots of power, I switched it off then on again and everything was back to normal.

Thanks for the help.

[632 Regal]

sounds like the stepper motors need rebuilding, common issue. http://www.wuffer.net/page5.html

[grave77]

are these the symptoms?

[grave77]

update - today the throttle seemed to hang more often, especially over 3K RPM I need to release my foot then step again to make it accelarate. or it feels like I crused it at that speed it stopped at.

[632 Regal]

just order the rebuilt set, at $125US it's a no brainer even if it dont help. your symptoms are the same with what I read. only thing is he charges a core til you send your old ones back. I saw a rebuilt set go for US $900.00 about a month ago.

the problem is they gunk up a bit at the brushes and dont get a good signal. I read and bookmarked a site but the work involved looks a bit complicated. If I have any problems like that I'll get the rebuilt set and send mine back instead of messing them up and making them worse.

[Wuffer]

The throttle bodies (DK's) on the V12 need to be cleaned anytime after 80K miles and sometimes sooner. As previously stated, they build up a residue of old grease and carbon dust from the brushes in the motor and can become quite sticky. R&R'ing DK motors is a relatively easy D-I-Y project but you should be prepared to replace the vacuum hoses (both large and small) that run from the DK's to the charcoal canister and fuel regulators. At 110K miles, the larger hoses especially will be very brittle and likely shatter when attempting removal. After installation a coast down procedure should be performed to synchronize the banks.
I do provide, as a service to the E31 community, refurbished DK motors on an exchange basis for $120/pair US including shipping via UPS Ground to any North American destination. New installation gaskets are also included. My only expectation is that cores be returned in a timely manner at your expense to me. I have a total of 8 sets available and in curculation at any time.
To learn more or to order a set, visit http://www.wuffer.net/page5.html or contact me direct at: wuffer@shaw.ca
Hope this helps!

[grave77]

Thanks mate, well I have already 2 DK motors on my old engine, one of them was very new from the way it looks also the metal color was still shining. so I will remove them and clean them, buy 2 gaskets and install them. then maybe I will fix the 2 old ones for future fixes. I didn't think that this is the symptom of a bad DK motor. if I failed I will send you 4 motors and get refurbished ones.

[shogun]

That is a very fair price, Wuffer.
I only hope that you always get back the old ones in time and without a problem.

I also have several pairs here which I refurbished for my friends in our E32 Club Japan.

[grave77]

for me it's a little expensive if I converted it to our local currency ... but I understood here that the electrical motor is the one that fails and needs fixing? or is it the mechanism gear that opens the throttle?

[shogun]

See my website, detailed info on DK cleaning. The worst examples I have seen
http://8810.teacup.com/750hiline/img/bbs/0000387.jpg
http://www.bimmerboard.com/members/shogun/original/dk750i.jpg
now cleaned
http://www.bimmerboard.com/members/shogun/original/dk750igereinigt.jpg
Here some more pics of cleaning
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-1c.jpg
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-2c.jpg
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-3c.jpg
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-4c.jpg
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-5c.jpg
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-6c.jpg
http://www.bimmerboard.com/members/shogun/original/drosselklappe_e32-7c.jpg
Technical data
http://www.bimmerboard.com/members/shogun/original/DK1.jpg
http://www.bimmerboard.com/members/shogun/original/DK2.jpg

[grave77]

so it's the brushes and the contact surface of the revolving rotor that fails.

are the brushes available for replacement at any BMW spare parts store? I need to fit in the same size from somewhere else?

[shogun]

Commutator, amature, brushes mainly inside.
If the engine sucked oil, you also have to clean it inside.

Note that some of the throttling valves have socalled tamper proof bolts. But these are also no problem to remove, just replace them with nice new ones.

Your dealer will have no spare part available for this, because this is 'tamper proof' secured.
I so far have never used a spare brush, just had to clean them.
The DK's are made by Bosch, so you may visit a Bosch shop for the brushes.
But I do not have a part number of that or a replacement.
That is no big problem, just measure it and find a replacement with same size. If you cannot find one, buy a slightly bigger size and file it to match.
Maybe Wuffer knows the part number of the Bosch brushes.

Then you can measure it, and make a function test if you want.
All nicely written down here
http://www.e31faq.com/attachments/att34.pdf

[grave77]

WoW ... this PDF got it all ...

I was wondering about the black rubber on the top of the DK motor, some cars had a hose connected to somewhere in the engine or a hose between the 2 DK motors, and most have it close by this rubber. I would love to know what is it for and why we see some difference between cars ( hose or plug )

[shogun]

That plug on top: that is for a disturbance air valve. That is for example in Germany necessary for passing the 2 years road test. The tester open this disturbance air valve and let's air inside to see how quick the system reacts and then checks the exhaust stuff. Here you can see it
http://www.bimmerboard.com/forums/posts/133398
And the lower small hose goes to the charcoal cannister and then to the tank back. There is also a valve in between to avoid dieseling.
I replaced all these hoses completely, they were brittle like glass.

Just found another nice thing on RF:
quote

And here is my DK test routine

Message: Use an old discarded PC power supply for the 4+ volts max to drive the DK. Works nicely to see if there are any hiccups in the operation of the DK at low voltage as it will reveal poor brush contact. I can also switch the polarity of the 12v take off on the top of the picture to test the seat motors.
http://members.roadfly.com/JNelson/DKTest1.JPG

------------------------
another good hint by Jon:
If you decide to clean your own DK motors keep in mind the source of the grease that contaminates the brushes. The throttle valves are assembled with a small amount of grease in the gearbox between the butterfly and the motor/wiper assembly. Although there is a small O-ring seal on the gearcase, grease still migrates up the helical gear and onto the brushes. So its not a bad idea to redistribute the grease in the gearbox and clean up the lower end of the armature shaft.

Jon
-------------------------
and Mark:
There is only really two wear items in the DK motor assembly - the feedback potentiometer and the brushes. The pot is a "wiper" design, and will eventually wear out, rendering the motor inoperative. The brushes wear down and coat the innards with carbon dust. The bearings are overbuilt, and the geartrain (on EML-II) is spring-loaded to eliminate lash due to geartrain wear. EML-III is a direct drive stepper motor (brushless, IIRC), which eliminates one more source of problems.

Why didn't Bosch and Siemens go with an optical position encoder? Sheesh.

Mark
--------------------------

[grave77]

I have a variable power supply with V/A meter so I can handle this. but I was looking at the last 2 images with the German data sheet/ diagram and I couldn't see the current draw. this might give a good idea if the DK is functioning properly or not, when I apply the supply I will watch the Ammeter and see the current flow, if it's more than it's supposed to be then I will know that I still have a problem.

I was wondering, how hard is it to upgrade the EML to EML III and put the stepper DK motors?! I always thought that the DKs are stepper motors until I saw the picture.

[shogun]

Just leave the system as it is, that is bullet proof. Just cleaning every 60 k or more is enough.
Basically cleaning the amature, the brushes (dust from the brushes) and the grease, that is enough.

[shogun]

If you need carbon brushes, go to your China Market in Dubai, they probably have it for cheap.
I know a shop in Germany which is specialized on these units for starters, generators, blower motors etc.
http://www.autokohlen.de/
for Bosch generators
http://www.technikline.com/pi-580964344.htm?categoryId=2
starters
http://www.technikline.com/pi1553376704.htm?categoryId=10
accessories
http://www.technikline.com/pi-1438736245.htm?categoryId=17

bearings for generators
http://www.technikline.com/pi1161098319.htm?categoryId=22
and so on